1957 Mushy Brakes

[35-709]

You will probably have to bleed the system again, although you can try it without bleeding if the master is bled and no fluid has come out of the lines where they connect to the master.  Figure on having to bleed the brakes again.

If this whole scenario happens again, talk to the overhauler and be prepared to send it back.  If the overhauler was you, take it apart and find the bad seal.

[savemy67]

Hello Johnny,

I may be misinterpreting your post, but when you bench bled the master cylinder and you said that "fluid came out strong", was the fluid from the outlet port of the master cylinder routed back into the master cylinder, or into a container with the end of the bleed tube constantly submerged?  If you bled the master cylinder, and fluid just spurted out of the outlet port (albeit strongly), then you most likely still have air in the master cylinder.

I generally bleed the longest brake line first.  This may or may not be the wheel furthest from the master cylinder.  It depends on the location of the brake line junction block at the rear axle.  I know that for models of the '60s, the adjusters are side specific.  So it is not just a matter of reusing the old adjusters, but putting them back on the side of the car from whence they came.  I am not sure about '57.

I would recommend that whenever a master cylinder is removed/replaced, you should bleed the system.

Respectfully submitted,
Christopher Winter

[60eldo]

  Hi thanks for your help. Yes when I bled it ,,,it just blurded out into a container because on the 57 master it has a filler tube hard to expliain, but I will try. So right now the master is in my garage in a vice. At the top is a hole where the fluid goes into it. I screwed in the fitting and above attached is a hose about 2 ft long that goes to a filler tube. I filled the tube and then at the front of the master is another fitting where the fluid comes out. I pressed the brake leaver and fluid came out into a clear plastic container.   PS I just ordered a used booster,,maybe it will work,,,maybe not,,am I frustrated,,,YES,,,anyone out there know this 57 system that I can call for      HELP!!!!

[wbdeford]

The shop manual procedure has you bleed the system at the booster (which sits up high) before moving to the wheel cylinders.  It doesn't even have a procedure for bleeding the master (which sits way down low).  I am thinking that if you are bleeding the system properly and it still isn't getting all the air out, that once you have a booster on the car and can follow the shop manual procedure, that it will be fine.

[Walter Youshock]

It because the master is bled THROUGH the booster.  Then the next step is bleeding the hydraulic portion of the booster then on to the cylinders.

[35-709]

He does not have a booster, it was previously removed.

[wbdeford]

He does not have a booster, it was previously removed.

He said he ordered one.

[35-709]

Right, but so far he has not had one.  I don't see why the master cannot be bench bled and then installed directly to the brake lines and the rest of the brakes bled as usual --- unless the master itself is faulty.

[35-709]

In his first post he described a firm pedal after replacing everything brake related, but then it went soft and finally to the floor.  With no visible leaks in the system and the master still full of fluid what else would it be other than a bad master that is leaking by the piston seal(s).   

[35-709]

OK, a complete shot in  the dark here.
If you pump the pedal do you get it back to firm again?  If, on your car, the master cylinder is below the wheel cylinders the fluid can actually get pushed back by the brake springs pushing on the wheel cylinders into the master requiring one or two pumps of the brake pedal to get the fluid and pressure back to actuate the wheel cylinders.  This would not happen with the Treadle-Vac installed since it is higher in the system.
This is why on older cars with hydraulic masters under the floor they sometimes have a residual pressure check valve (not the proportioning valve) that actually keeps a small amount of positive pressure in the system to keep it ready but not enough pressure to actually activate the drum brakes.  If the master is on the same level as the wheel cylinders or above, there is not a problem, only if the master is lower.  With the car level determine if the master is lower than the wheel cylinders.  If pumping the pedal does not return it to firm then this post is probably for naught and we are back to square one.
The residual pressure check valves are readily available and inexpensive, street rod and resto-mod builders use them all the time on old cars when they upgrade but keep the master under the floor.     

[35-709]

I keep thinking about this --- my post above is not necessarily to encourage adding residual pressure valves to your system, even if that would fix the problem.  I too believe, as others do, that the Treadle-Vac should be put back and the system returned to stock for serviceability and safety. 

[Walter Youshock]

Unfortunately it's a hydro vac.  Last year Cadillac used it and it's gotta be from a 57.

[60eldo]

    OK I just called the company that rebuilt the master and they are sending a courier out tuesday to pick it up and re-inspect it. Thats great. Hopefully they find a problem,,,I will let you guys know By the by, I just bought a hydro-vac used today. I dont know weather Im gonna use it or not, right now. Id like to see if I can get good brakes without it 1st. The guy I bought it from says he took it out of a 57 and theres fluid inside. Also to answer question above, the car was sitting on jack stands when bled, so the master would have been higher. I had a good pedal at that point. But once the wheels were put on and car was lowered, I started loosing firmness

[35-709]

I didn't have it quite right in my Reply #29, I kept thinking of my '35 which has a modern underfloor master and 4 wheel disc brakes.  Cars with drum brakes need a residual pressure valve no matter where the master is located because the brake springs will push the fluid back out.  The master often has that residual built in but on yours the residual pressure valve may be part of the (sorry) Hydro-Vac, I just don't know.  Point is, you should have 2 residual pressure valves in the system, one to the front shoes and one to the rear, if they are incorporated in the Hydro-Vac then you need to add them as long as you don't have the Hydro-Vac installed, they may be in the master which is a good question to ask your rebuilder.  Guess I'm tapped out on this one.

[Dave Shepherd]

Working on the same car in my shop, I took the cover off a new master and used a line from the port right into the reservoir to bleed it, then plugged the port and reinstalled the cover. You might get a pedal when bleeding the brakes but there is no residual valve in that master, hooked directly to the brake system the car barely stops at low speeds and yes  it must be pumped to bring the pedal up some.

[Coupe Deville]

Reading your post, I was going to say that your problem was the booster. I rebuild and resleaved the master cylinder on my 57' and I had the same problem, and It was the booster. I eventually converted the car to my own dual reservoir master cylinder set up, with a modern booster/master combo. I couldn't afford to get the original booster rebuild or replaced at the time, so I made my own coversion. So now if your just running manual brakes bypassing the stock system, and plan to keep it that may for a while, honestly I would ditch the stock master cyclder find the biggest bore diameter master cylinder for drum brakes and put that in place of the stock one. It would be easy to make up some brackets to put a new master in and mount it on the frame. Heck, might as well just put in a 4 wheel drum brake dual reservoir master in for safety, and for a little better braking performance. The stock master cylinder on this car is painfully small. So it can be bypassed, but I would swap it out with something better if I was going to stay with manual brakes. On the Bendix Hydrovac system on the 57' I think the master cylinder really only actuates a second diaphragm on the booster, and the booster provides a majority of the braking power. I always thought of the master cylinder like a slave cylinder, since all of the magic happens in the booster on this system. The Bendix hydrovac brakes on the 1957 Cadillac is quite a crazy, complicated, misunderstood system.
I did the best and safest job I could do when I had my 57' Sedan before I sold it. But I'm glad it didn't have the hydrovac on it when I sold it. Best of luck with it.

-Gavin

[60eldo]

  This is how I plan to bleed my master when it comes back. Keep filler tube full at all times. Slowly press in brake rod til all air comes out, then cap it so no air comes in. I will install it with filler tube connected,,,,thoughts?

[savemy67]

Hello Johnny,

Keep the filler tube full, and the hose/tube submerged in the jar.  Bleed until no air bubbles appear in the jar.  If the outlet to the jar is a rubber hose, pinch it off when done.  If it is a metal tube, when you disconnect it, you may get a small amount of air in the M/C.  You should be able to bleed this out when all the lines are connected.

Christopher Winter

[buefchris]

You need the remote HYDRO-VAC with this brake system. It sends the pressure to the wheel cylinders(like a second master cylinder).
They did it this one year and then changed to a Treddle vac system the next year. Lucky you.

[60eldo]

   OK,,,Im back. I installed a used booster today, bled the top bleeder then the bottom one, then re attached the brakeline.,,,I have brakes,,,,BUT feels like stand brakes not power,,,,how do I know if the booster is working,,,,pedal is good but I have to push hard to stop,,,whats up,,,what did I do wrong